Apparatus for applying a liquid coating to a moving object



y 3 L. J-B. FORBES 1,909,260

APPARATUS FOR APPLYING A LIQUID COATING TO A MOVING OBJECT Filed 9, 1932 Patented May 16 1933 UNITED STATES PATENT OFFICE LEWIS mam JI'OBIBES, or G1. mremn I mm'rus iron mnme a mom ooa'rm'e' r '1 IOVDTG onmc'r Application fled Kay 8, 1988, lerlal Io. 810,810, and in Great Britain. April 88, 1981.

This invention relates-to a method of and apparatus for ap lying a'liquid coating to s a travelling flat o ject and has for its object an improved method and apparatus for applying an even coating.

' The invention will be described with reference to a horizontal travelling strip, which may be continuous or composed of-a succession of plates or sheets.

19 A spray gun of ordinary type is employed,

in which air is used to form the s ray, and the gun contains a valve which can opened or closed to start or stop the spray. This spray control valve is commonly operated pneumatically and the invention will be described firstly with reference to such a valve,

but it is applicable to guns having valves operated electrically or mechanically.

According to the invention, the"gun is carried on a spindle and is rotated thereby in a plane parallel to that of the travelling strip in a circle of substantially greater diameter than the width of the strip and the controlling valve ofthe gun'is operated intermittently, so that the gun delivers a spray only during either one or both of its two passages over the strip in each revolution.

If the diameter of the circle of rotation of the spray gunwere equal to the width of the. strip, the edge of the strip would receive a much thicker coating then the centre. The coating, however, is of substantially even thickness if the diameter of the circle of rotation is substantially greater than'the width of the strip, so that the arc during which the n is over the strip during each passage 1s substantially less than 180..

The invention further comprises means whereby the arc (11111125 liversh a spray can be justed to any desired 1%: the accompanying drawing Figure 1 is an elevation, partly in'section,

of the apparatus;

Figures 2, 3 and 4 are plan views, partly in section, of portions of the air valve device;

Figu

re 5 is a plan view of the modification, partly in section, of a gun with spray it is led to the annular space 22. The which the gun decontrol valve adapted'for mechanical op- Maiden, and

Figure 6 is a diagrammatic plan view of the modified form of the gun ada ted for mechanical operation. and s owing t e travelling strip. p

In the apparatus as shown in Figures 1 to 4, two spray guns, diametrically opposite each other, are used, but the operation of one gun is similar to that of the other.

The. as 1 are attached by clips 2 to rods 3- whic are attached by clips 4 to radial arms 5 projecting from the spindle 6. By means of the clips 2 and 4, the gunsfiiay be adjusted respectively in height and in radial position. -The spindle 6 is rotatably supported in a bearing 7 and is rotated by the worm wheel 8.

The liquid to be sprayed is supplied through the pipe 9 and sleeve 10 to passages in the spindle (not shown) to which are connected flexible pipes 11 leading to the guns. The air for spraying the liquid is supplied through the pipe 12 and sleeve 13' to assages in the spmdle (not shown) to WhlOh are connected flexible pipes 14 leading to the guns. j

The spray gun valves are operated by air pressure delivered through pipes 15 and passages 16 in'the spindle terminating in holes 17 in the plate 18 on the spindle. as'will be clear by reference to Figures 1, 2 and 3.

An air valve'controlling the supply of air pressure consists of three parts, the late 18, the air valve body-19 (Figures 1 and 3) and the cover 20 (Figures 1 and 4). The air under pressure is led to the air valve body 19 by a flexible pipe attached at 21, whence. ace 22 is closed below by the plate 18 and above by the cover 20. The passages 16 to the spray control gun-valves open into the space 22 at 17. The space 22 has an opening 23 to the atmosphere and it is divided into two portions by the web 24.

The .air valve comprising 18, 19, 20, as shown is provided with means for varying the are through which the gun is operated to spray. In certain cases, however, as, for instance, when the object to be coated, is always of the same width. it is not necessary that the arc of operation should be variable. The ac tion of the air valve will be described first on the assumption that it provides only for a fixed arc of operation. In this case the annular space 22 is bridged by a second web 25, shown in dotted lines in Figure 3, forming with the web 24 aclosed space 26. In the position shown in Figure 3, this space 26, under air pressure ironithe inlet 21, is connected with one of the guns by the hole 17, and the gun is then operating to spray. As the spindle 6 with its plate 18 rotates, for example, clockwise as seen in Figure 3, when the hole 17 passes under the web 25 and opens into the space 26, the gun starts to operate. When the hole 17 comes under the web 24 and opens 1 into the long annular space on the other side ceases to operate.

of the web, it is in communication with the atmosphere through the opening 23, whereby the air pressure is released and the gun The are of operation is therefore determined by the length of the space'26 between the webs 24 and 25.

. In the air valve as shown the arc of operation is made variable as followsz-The piece 25 is not a web integral with the walls of the annularspace 22 but is fixed to the underside of the cover 20, as shown in dotted lines in Figure 4. This cover is capable of being turned relatively to the body 19, being held in any desired relative position thereto by studs fixed in the holes 27 of the body19, which enter slots 28 in the cover and are locked thereto by nuts 29.

By turning the cover 20 relatively to the body 19, the position of the piece is varied and therefore the point at which the operation ofthe gun starts is varied. 1

Now the body 19 is held in position by rods 30 which are locked by nuts 32 to a plate 31 ing holes 33 in lugs 34: on the body 19. The rods 30 pass through circular slots in the plate 31, so that, on slackening the'nuts 32, the body.

19 can be turned to any desired position. By

so turning the body 19, the position of the web 24 is varied and therefore the point at which the operation of the gun ceases is varied.

Since the cover 20 turns with the body 19, the adjustment is efiected in practice by first turning the body 19, to adjust the point at which the gun ceases to o crate and then turning the cover 20 to ad ust the point at which it starts to operate.

The cover 20is pressed against the body 19, and this against the plate 18 by the spring 35.

In the. embodiment of: the invention illustrated in Figures 5 and 6 an arrangement is provided wherein the spray gun is controlled by a mechanically o erated valve. This form of apparatus utilizes a rotating mechanism similar to that employed in the embodiment of Figure 1 but with the omission of neonate the air control valve comprising 18, 19, 20. Figure 5 is a horizontal section of one gun as taken along the line A of Figure 1, but

with the gun held on the far side of the rod star wheel 3?, e being the spindle, 38 the strip to be coated, and 39 the path of the gun. At each side of the strip 38, pins d0, supported on brackets ll are held in position to engage the star wheel 37. The brackets are tired to the framework of the strip conveyor by bolts 42 engaging circumferential slots 43 in the brackets 41 and approximately radial slots 44 in the framework. The pins 10 can thereby be adjusted in position to cause operation of the gun through any desired arc of contact.

If the arc of travel of the gun be fixed, such as would be the case, for example, in the embodiment of Fig. 1 if the gun control valve 18, 19, 20 was not adjustable it is still possible to operate the apparatus for varying widths of strip, by varying the radial position of the gun. This, however, is inconvenient in practice because the thickness of coating is varied thereby, and this can be corrected only by varying the travelling speed of the strip. This, again, varies the overlap of the successive bands of liquid sprayed, and the overlap rotation of the spindle.

When, however, the arc of operation is variable, as in the apparatus shown, variation of this are is the only adjustment which has to be made for varying widths oi strip. fixed to the bearing block 7, the rods 30 enter- The are of operation of 109, as shown approximately in Figure 6, is found to give substantially uniform thickness of coating and the arc can be increased beyond this to give a coating sufficiently uniform for many purposes.

If, in increasing the arc oi operation to suit increasing width of strip, the permissible limit of arc would be passed, the necessary adjustment must be made by increasing the radius of the gun.

It is therefore preferable that the s eed of rotation of the gun and the speed 0 travel of the strip should be variable. i llt is generally more convenient that thegun should be operative to spray during only one of its assages over the object in each revolution, ut it may be made operative during both passages to give a. double coating.

Having described my invention, I declare that what 1 claim and desire to secure by Letters Patent is I v 1. Apparatus for coating a traveling flat object, comprising a gun for spraying the has to be corrected by varying the speed oi coating 1i uid, means for moving the gun over the o ject, said gun having a valve to control its operation," a rotary spindle, an arm secured to the spindle and carrying the gun at a radius substantially greater than half the width of the object, means for rotating the spindle to move the gun in'a circular path inia plane parallel to that in which the object is moved, and means coaxial with said spindle and mounted thereon for actuating the controlling valve to operate the gun only during the part of therevolutionary movement of the gun when it travels over the object.

2. Apparatus for coating a traveling flat object including a gun spraying the coating liquid by air, means for moving said gun over the object, comprising a spindle carryrot-ating the spindle to move the gun in a plane parallel to that in which the object is -moved, a valve on-the spindle for controlling the operation of the gun, means also on the spindle for actuatin the controlling valve to operate the gun on y during one of its passages over the object in each revolution, and means for adjusting the length of arc. on each revolutionduring which the gun is in operation.

3. Apparatus for coating a travelingflat object comprising a gun spraying the coating liquid. by air, a pneumatically actuated valve for controlling its operation, means for moving the gun over the object, comprisin a spindle carrying the gun at a radius 1 su stantially greater than half the width of the object, means for rotating the spindle to move the gun in a plane parallel tothat' in which the object is moved, and a valve mounted. on the spindle whereby a passage in the spindle communicating with the controlling valve is alternately, .by rotation of the spindle, put into communication with a source of air under pressure other than atmospheric and with the atmosphere;

Y 4. Apparatus as in claim 3in which a sleeve in the valveon the spindle is adjustable to vary the relative time duringwhich the controlling valve is in communication with the source of air under pressure other than "atmospheric and with the atmosphere.

5. Apparatus for coating a traveling flat object including a gun for spraying coating, a'st-ationary member, a rotary spindle supported by the stationary member, an. arm

inoperative during movement over designated parts of its path.

,7. Apparatus for coating a traveling flat object with a uniform thickness of coating,

.including a gun'for spraying the coating,

means to support the gun for movement over the object in a plane parallel to the path of travel of the flat object, said supporting means including a rotary spindle, means for rotating the same, and a rigid arm secured to and rotatable with the spindle and projecting radially therefrom, said gun receiving ,its entire support from said arm and being secured thereto whereby its path of travel in'each cycle will be a circle, said circular path extending beyond the edges of the object and having a radius substantially greater than half the width of the object, and' control means for the gun and means for actuating said control means whereby the coating is applied to the traveling-object during movement of the gun over a partxofits path in the form of successive curved stripes defined by the arc of a circle of substantially greater diameter than the width of the object. 1

8. Apparatus for coating objects comprising a gun for spraying the coating liquid, a pneumatically actuated valve controlling operation of the gun, supporting means for the gun including a rotatable spindle, means nature hereto.

LEWIS JEX-BLAKE FORBES.

secured to and rotatable with the spindle carrying the gun for movement over the object along a curvilinear path in a plane parallel to the path of travel of the object, means to rotate the spindle,.a valve on said spindle I for controlling operation of the gun, and

means also on the spindle for actuating the.

control valve to render the gun operative 

